defmodule Plug.Parsers do
defmodule RequestTooLargeError do
@moduledoc """
Error raised when the request is too large.
"""
defexception message: "the request is too large. If you are willing to process " <>
"larger requests, please give a :length to Plug.Parsers",
plug_status: 413
end
defmodule UnsupportedMediaTypeError do
@moduledoc """
Error raised when the request body cannot be parsed.
"""
defexception media_type: nil, plug_status: 415
def message(exception) do
"unsupported media type #{exception.media_type}"
end
end
defmodule BadEncodingError do
@moduledoc """
Raised when the request body contains bad encoding.
"""
defexception message: nil, plug_status: 415
end
defmodule ParseError do
@moduledoc """
Error raised when the request body is malformed.
"""
defexception exception: nil, plug_status: 400
def message(exception) do
exception = exception.exception
"malformed request, got #{inspect exception.__struct__} " <>
"with message #{Exception.message(exception)}"
end
end
@moduledoc """
A plug for parsing the request body.
This module also specifies a behaviour that all the parsers to be used with
Plug should adopt.
## Options
* `:parsers` - a set of modules to be invoked for parsing.
These modules need to implement the behaviour outlined in
this module.
* `:pass` - an optional list of MIME type strings that are allowed
to pass through. Any mime not handled by a parser and not explicitly
listed in `:pass` will `raise UnsupportedMediaTypeError`. For example:
* `["*/*"]` - never raises
* `["text/html", "application/*"]` - doesn't raise for those values
* `[]` - always raises (default)
All options supported by `Plug.Conn.read_body/2` are also supported here (for
example the `:length` option which specifies the max body length to read).
## Examples
plug Plug.Parsers, parsers: [:urlencoded, :multipart]
plug Plug.Parsers, parsers: [:urlencoded, :json],
pass: ["text/*"],
json_decoder: Poison
## Built-in parsers
Plug ships with the following parsers:
* `Plug.Parsers.URLENCODED` - parses `application/x-www-form-urlencoded`
requests
* `Plug.Parsers.MULTIPART` - parses `multipart/form-data` and
`multipart/mixed` requests
* `Plug.Parsers.JSON` - parses `application/json` requests with the given
`:json_decoder`
This plug will raise `Plug.Parsers.UnsupportedMediaTypeError` by default if
the request cannot be parsed by any of the given types and the MIME type has
not been explicity accepted with the `:accept` option.
`Plug.Parsers.RequestTooLargeError` will be raised if the request goes over
the given limit.
Parsers may raise a `Plug.Parsers.ParseError` if the request has a malformed
body.
## File handling
If a file is uploaded via any of the parsers, Plug will
stream the uploaded contents to a file in a temporary directory in order to
avoid loading the whole file into memory. For such, the `:plug` application
needs to be started in order for file uploads to work. More details on how the
uploaded file is handled can be found in the documentation for `Plug.Upload`.
When a file is uploaded, the request parameter that identifies that file will
be a `Plug.Upload` struct with information about the uploaded file (e.g.
filename and content type) and about where the file is stored.
The temporary directory where files are streamed to can be customized by
setting the `PLUG_TMPDIR` environment variable on the host system. If
`PLUG_TMPDIR` isn't set, Plug will look at some environment
variables which usually hold the value of the system's temporary directory
(like `TMPDIR` or `TMP`). If no value is found in any of those variables,
`/tmp` is used as a default.
"""
alias Plug.Conn
use Behaviour
@doc """
Attempts to parse the connection's request body given the content-type type
and subtype and the headers. Returns:
* `{:ok, conn}` if the parser is able to handle the given content-type
* `{:next, conn}` if the next parser should be invoked
* `{:error, :too_large, conn}` if the request goes over the given limit
"""
defcallback parse(Conn.t, type :: binary, subtype :: binary,
headers :: Keyword.t, opts :: Keyword.t) ::
{:ok, Conn.params, Conn.t} |
{:error, :too_large, Conn.t} |
{:next, Conn.t}
@behaviour Plug
@methods ~w(POST PUT PATCH DELETE)
def init(opts) do
parsers = Keyword.get(opts, :parsers) || raise_missing_parsers
opts
|> Keyword.put(:parsers, convert_parsers(parsers))
|> Keyword.put_new(:length, 8_000_000)
|> Keyword.put_new(:pass, [])
end
defp raise_missing_parsers do
raise ArgumentError, "Plug.Parsers expects a set of parsers to be given in :parsers"
end
defp convert_parsers(parsers) do
for parser <- parsers do
case Atom.to_string(parser) do
"Elixir." <> _ -> parser
reference -> Module.concat(Plug.Parsers, String.upcase(reference))
end
end
end
def call(%Conn{req_headers: req_headers, method: method,
body_params: %Plug.Conn.Unfetched{}} = conn, opts) when method in @methods do
conn = Conn.fetch_query_params(conn)
case List.keyfind(req_headers, "content-type", 0) do
{"content-type", ct} ->
case Conn.Utils.content_type(ct) do
{:ok, type, subtype, headers} ->
reduce(conn, Keyword.fetch!(opts, :parsers), type, subtype, headers, opts)
:error ->
%{conn | body_params: %{}}
end
nil ->
%{conn | body_params: %{}}
end
end
def call(%Conn{body_params: %Plug.Conn.Unfetched{}} = conn, _opts) do
conn = Conn.fetch_query_params(conn)
%{conn | body_params: %{}}
end
def call(%Conn{} = conn, _opts) do
Conn.fetch_query_params(conn)
end
defp reduce(conn, [h|t], type, subtype, headers, opts) do
case h.parse(conn, type, subtype, headers, opts) do
{:ok, body, %Conn{params: %Plug.Conn.Unfetched{}, query_params: query} = conn} ->
%{conn | body_params: body, params: query |> Map.merge(body)}
{:ok, body, %Conn{params: params, query_params: query} = conn} ->
%{conn | body_params: body, params: params |> Map.merge(query) |> Map.merge(body)}
{:next, conn} ->
reduce(conn, t, type, subtype, headers, opts)
{:error, :too_large, _conn} ->
raise RequestTooLargeError
end
end
defp reduce(conn, [], type, subtype, _headers, opts) do
ensure_accepted_mimes(conn, type, subtype, Keyword.fetch!(opts, :pass))
end
defp ensure_accepted_mimes(conn, _type, _subtype, ["*/*"]), do: conn
defp ensure_accepted_mimes(conn, type, subtype, pass) do
if "#{type}/#{subtype}" in pass || "#{type}/*" in pass do
%{conn | body_params: %{}}
else
raise UnsupportedMediaTypeError, media_type: "#{type}/#{subtype}"
end
end
end